Use of MeV O+ ion implantation for isolation of GaAs/AlGaAs heterojunction bipolar transistors

Abstract
The implant isolation characteristics of highly doped n‐ and p‐type GaAs epitaxial layers implanted with 5 MeV O+ ions are reported. High (∼108 Ω/⧠) sheet resistances are obtained in such layers following annealing at 550–600 °C for ion doses around 1015 cm−2. The residual conductivity is still due to hopping processes with small activation (50–70 meV) energies. The use of a single MeV O+ implant considerably simplifies the isolation of GaAs/AlGaAs heterojunction bipolar transistor (HBT) structures relative to the usual multiple‐implant keV energy scheme. Small geometry (2×5 μm2) HBTs with gains of 25 for highly‐doped (p=7×1019 cm−3) base layer structures have been fabricated using MeV implant isolation.

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